What Causes Algae and Other Pond Problems?

Algae, excessive aquatic plants, cloudy or murky water, odors and even lethargic fish are all problems that pond owners face, but what causes these problems?

Simply stated, ponds with such problems have an ecosystem that is out of balance. This unequal balance is generally caused by too many available nutrients in the water and low oxygen content. Nutrients come from a variety of organic matter that is commonly found in ponds like dead leaves, grass clippings, fish food, fish and animal waste, dead algae and aquatic plants, fertilizer run-off and all sorts of other organic materials. The organic waste releases nutrients that are used by aquatic plants like algae, hydrilla, duckweed and other aquatic nuisance plants to grow and thrive. When excessive levels of nutrients are present these plants can grow fast and quickly take over a pond.

Normally a pond with a sufficient dissolved oxygen level will be able to break down and decompose the organic matter before it can be utilized by pond plants, however, ponds with lower oxygen levels will be slower to react and the organic matter will build. Eventually a situation will occur in which the break down of the waste will put a such a strain on the ponds oxygen level that the marine life, like fish, will become negatively impacted, due to the lack of dissolved oxygen available to them. In extreme cases there can be such low oxygen levels that fish kills occur.

In addition to the dead organic materials creating a strain on the oxygen levels, excessive outbreak of algae can have the same effect. Normally a small amount of algae is ok because pond plants like algae do release oxygen back into the water. It is when algae outbreaks get severe, that they too affect the pond's oxygen level. During daylight hours, algae consume carbon dioxide from the water and release oxygen, but when night falls, this process is reversed and the algae begin utilizing the ponds oxygen to survive. So when there is a large algae population, oxygen levels can be significantly reduced in the over night hours leading to increased algae growth during the day.

Another byproduct of the cycle of poor organic material breakdown is the increased presence of odors. Material that is slow to breakdown can become anaerobic and emit pungent and noxious gases like ammonia and hydrogen sulfide. Again, under normal conditions where a pond has a healthy oxygen level, the matter is digested aerobically and no odor is produced, but when there is not enough oxygen to do the job, anaerobic microbes begin digesting the waste, creating the odors.

Aeration, often times can be a successful remedy for many pond problems. An increased in available dissolved oxygen can reverese many of the problems above. Aerobic bacteria that are both naturally present and those that are added are stimulated by additional oxygen and become more aggressive at decomposing and removing organic muck and sludge which can accumulate in the bottom of ponds creating an unhealthy and malodorous environment. Aeration will also help circulate and mix water which helps to eliminate stratification and also create and environment unfavorable to algae. Efficient aeration can also help prevent fish kills when and uncontrollable event happens such as a sudden algae bloom die-off or an influx of waste from a heavy rain that can normally strain an un-aerated pond.

Make no mistake, a harmonious balance between nutrients and oxygen is not the end-all be-all solution to all pond problems. Certainly there are diseases and other ailments that are started by other reasons, but having a healthy, stable pond environment goes a long way in preventing pond problems.